Downloaded and compared, no changes...

 

@V8Cowboy

I predict a bump in mpg's on the work commute. Calculated load dropped on the only "flat" section of the drive in (approx 2 miles) as well as intake manifold vacuum increased. MAP was always 12.5-13.5 inhg, now 14-15 inhg. Using CC to keep my foot out of it.

 

18.7 mpg (18.689)... over 250.2 miles. The work commute is 68 mi RT x3 =204 miles + 46.2 extra miles in & around town. The work commute was using CC most of the time, there were a few times I had to go around others but I behaved myself well lol.

Not bad!

 

Doing a 2nd work commute mpg test with the PL mod ball valve adjusted... positioned for more bottom end torque.

 

Update because of what I see compared to tanks in the past... so in general, with the fuel gauge having been previously corrected to match fuel used (half tank = 12 gal from a 24 gal tank), I usually see 75~80 miles at the 7/8ths tank mark & 100~110 at the 3/4 tick mark on the gauge. I always count the miles when the gauge needle is half way off the tick mark for consistency. This morning getting to work I'm seeing a very different picture... This already exceeds what I saw on the last tank, granted the last tank had mixed miles on it (city/hiway) but still, this raises an eyebrow... Be reminded I have the ball valve for the PL in the full open position on this tank, previous tank was closed.




Pic of engine as it sits, you cant see the air box where I opened up both ends and inserted the sheet metal divider that controls flow into the air filter...

 

Another thing to mention.. Over on the diesel form I'm at often I've discussed making a test setup to help me test different air box & intake tube setups. There is a lot to be had by adding the turning vane on the inside of the intake tube (has to be made correctly!!!). I also have an aero mod mpg thread over there where I tried a lot of things in an effort to improve mpg's. During a discussion recently I realized the setup I plan to do for the intake tube testing could also be leveraged to test a tailgate spoiler design I have in mind. I have a metal shop working up a quote for me on the design with the up-front disclosure that I have to test it 1st before I build. The goal is to design the spoiler similar to what is on the ram but with design changes geared towards reducing the aero drag bubble that sits behind the truck. If this works on the Dak, then the Ram will get one as well.

This is how the Ram looked after an 11 year 345k (currently has 502k on it) makeover I did years back, it is the same today but with different tires (same size) and no tonneau cover (broke, needs to be fixed). On a 600+ mile trip a while back before losing the tonneau cover, the return trip saw high speeds >75 mph for extended periods. The mpg's out of that tank on the return trip ended up at 19.99x mpg. Was absolutely shocked it was that high but... the numbers don't lie. this truck (diesel) has a vented fuel tank which allows me to fill it up to the neck every time with consistency. This truck I also tune with HP Tuners and have it dialed in for the mods I installed.



One lesson learned here is the gap between the cab & bed, a seal right there will keep the flow attached and the boundary layer small which will reduce drag. if you look at the top of the rear bumper, follow that body line to the cab. The seal installed goes from the top of the bed down to that body line, anything lower & airflow goes right into the bumper adding drag.

food for thought...

 

19.692 mpg, all commute miles over 3 days, 220.5 miles. Speeds = 63-67 mph (passing)

 

A buddy of mine had mentioned that the back pressure thing is a myth for mpg's. Having gone thru what I just did, I'd have to agree. My Dak with the boat anchor tire/wheel combo just turned its 4th best mpg tank (maybe 3rd... would have to go look for the number for the race weekend, that was 19 something as well). It also is putting out some really awesome power as it sits w/o the tune tweaked. This has been a fun journey so far with just a few things left that I plan to play with. One of which is in the HPT tune in the transmission pages, a torque table. The other 2 are the OEM sized tires with speedo recal & the rear tailgate spoiler. My original goal was to get 20 mpg's out of this truck, stated that in post #1. I already know that if I dial back the fuel pressure compensation mpg's will go up a tad bit, same as if I'd adjusted the injector pulse width. I plan to go datalog this tune & fine tune it. Will most likely adjust the FP setting and see cause & effect in back to back runs. Unfortunately there is too much traffic in this area these days to do this during the day, which leaves early mornings. Not really a problem for me but it would be on days where I'd actually get to sleep in (usually up at 0330)

With that said, this thread has kind of turned into a build thread so I might as well keep that info in here as well when I get those done.

 

Retune done, dialed back power/fueling in the cruise zone below 2100 rpms. Part throttle manners are better. While the power drop will be missed, to be honest its way more than what is needed for how i need the truck.

Will see Thursday if there is an mpg bump (210+ work commute miles)

 

19.033 mpg's over 225+ miles (5th 19.x or better tank on this truck... Should also note that the 2 day fill last week was a 17.9 mpg, all work miles. I suspect the fuel trims were still getting tweaked on the 19.6 tank.

Going to do more tweaks to the tune this weekend & continue the eval. On travel next week so it will be a while before I can get back to this.